durmast oak

Superficially a compound of durmast +‎ oak, but the origin of durmast is unclear and possibly a result of scribal error. The first edition Oxford English Dictionary suggests that Thomas Martyn's dictionary for gardeners and botanists (1798) originated the word through misreading dun mast ("light-brown acorn"), an interpretation also suggested by some earlier works going back to at least 1836, although a connection to Welsh derw (“oaks”) has also been suggested.